No disrespect meant to PawelDecowski at all (his CC number validator looks awesome, I'd use it) but he couldn't monetize it even if they he wished to -- too much competition in that space. Nobody is going to even pay $1 when they can just go on GitHub and find several similar libraries which do somewhat similar things.

I think £55 a year is best case scenario. At least it likely covers web-hosting costs.

You can absolutely charge money for this if you solve a painful problem for businesses: http://creditcardjs.com

But you're still up against freely available libraries that let a web developer build similar functionality, as as jquery.payment from the folks at Stripe:

https://github.com/stripe/jquery.payment

While it's not a completely like-for-like comparison, I suspect it will be tough to justify $299 per single web site for many businesses that might use these tools in the first place. Personally, I'd want solid data about conversion rates to back up the marketing on the creditcard.js website before I'd consider spending real money on anything like this.

Some companies value the support you may need over initial cost.

It only validates the number. It doesn't take part in the actual transactions.

Still, it helps.